The present invention relates to a master making and feeding device for a printer and more particularly to a master making and feeding device capable of perforating a stencil with heat and feeding the perforated stencil or master to a print drum.
A thermal digital printer using a stencil (stencil printer hereinafter) is extensively used as a simple printer. A stencil printer includes a thermal head having a plurality of fine heat generating elements arranged thereon in the main scanning direction. The head is brought into contact with a thermosensitive stencil, which includes a thermoplastic resin film, via a platen roller. While the stencil is conveyed, the heat generating elements are selectively energized to perforate the stencil with heat in accordance with image data, thereby making a master. After the master has been wrapped around a porous print drum, ink is fed to the drum from the inside of the drum. A press roller, press drum or similar pressing means presses a paper sheet against the print drum via the master. As a result, the ink oozes out via the print drum and the perforations of the master to thereby print an image on the paper sheet.
A master making and feeding device feeds the perforated stencil to the print drum. It is a common practice with a master making and feeding device to use a single stepping motor or drive means for driving a platen roller, a stencil set roller, a tension roller pair, and a turn roller pair, as taught in, e.g., Japanese Patent Laid-Open Publication Nos. 9-226088, 10-181177 and 11-91227. The stencil set roller corresponds to a pay-out roller 40 shown in FIGS. 2 and 3 of Laid-Open Publication No. 9-226088 mentioned above. The tension roller pair corresponds to a first conveyor roller pair 72 taught in Laid-Open Publication No. 11-91227. Further, the turn roller pair corresponds to an upper and a lower turn roller 7 and 8 taught in Laid-Open Publication No. 9-226088 or to a second conveyor roller pair 74 taught in Laid-Open Publication No. 11-91227. The turn roller pair plays the role of conveying members for feeding the leading edge of the perforated stencil to the print drum. Drive transmission from the stepping motor to the turn roller pair is selectively set up or interrupted by a solenoid-operated clutch at a timing different from a timing assigned to the platen roller. This kind of master making and feeding device, however, has various problems left unsolved, as will be described in detail later.
Technologies relating to the present invention are also disclosed in, e.g., Japanese Patent Publication No. 7-97813, Japanese Patent Laid-Open Publication Nos. 4-189544, 10-157052, 10-202996, 6-247031, 9-216448 and 5-201115, Japanese Utility Model Publication No. 2-274, Japanese Patent Laid-Open Publication Nos. 11-20295, 7-17013 and 61-287781, U.S. Pat. Nos. 5,816,149, 5,740,731, 5,782,179 and 5,970,869, and U.S. Ser. Nos. 08/926,423 and 09/014,269.
It is therefore an object of the present invention to provide a master making and feeding device for a printer capable of capable of producing a print faithfully representative of a document image, and reducing a first print time (FPT) while allowing a stencil to be conveyed by a platen roller in a constant amount.
A master making and feeding device for a printer of the present invention includes a first conveying section including a rotatable platen roller for pressing a stencil between a master making device and the platen roller to thereby thermally perforate the stencil, and conveying the perforated stencil to the downstream side in the direction of stencil conveyance. A second conveying section is arranged between the first conveying section and a print drum, around which the perforated stencil is to be wrapped around, for conveying the perforated stencil conveyed by the first conveying section toward the print drum. A conveyance drive section drives, at a preselected timing during or after the perforation of the stencil effected by the first conveying section, the second conveying section to thereby feed the leading edge of the perforated stencil to the print drum. The conveyance drive section drives the second conveying section such that the second conveying section conveys the perforated stencil at a higher speed than the first conveying section.